Recursive CTE with partition by column - sql-server

Question

Below are the table structure
drop table if exists #Transactions
create table #Transactions (TID int, amt int)
insert into #Transactions values(1, 100)
insert into #Transactions values(1, -50)
insert into #Transactions values(1, 100)
insert into #Transactions values(1, -100)
insert into #Transactions values(1, 200)
;WITH y AS
(
SELECT TID, amt, rn = ROW_NUMBER() OVER (ORDER BY TID)
FROM #Transactions
), x AS
(
SELECT TID, rn, amt, rt = amt
FROM y
WHERE rn = 1
UNION ALL
SELECT y.TID, y.rn, y.amt, x.rt + y.amt
FROM x INNER JOIN y
ON y.rn = x.rn + 1
)
SELECT TID, amt, RunningTotal = rt
FROM x
ORDER BY x.rn
OPTION (MAXRECURSION 10000);
This is similar to question recursive cte with running balance
But I need to running balance for each TIds..suppose if I insert to following transaction of TId=2
insert into #Transactions values(2, 100)
insert into #Transactions values(2, -50)
insert into #Transactions values(2, 100)
insert into #Transactions values(2, -100)
insert into #Transactions values(2, 200)
I need to achieve same only in recursive CTE method without lots of modification.. Please suggest a solution

Answer 1

You need to handle TID in your ROW_NUMBER() window function and also CTE JOIN
;WITH y AS
(
SELECT TID, amt, rn = ROW_NUMBER() OVER (PARTITION BY TID -- <= added here
ORDER BY TID)
FROM #Transactions
), x AS
(
SELECT TID, rn, amt, rt = amt
FROM y
WHERE rn = 1
UNION ALL
SELECT y.TID, y.rn, y.amt, x.rt + y.amt
FROM x INNER JOIN y
ON y.rn = x.rn + 1
AND y.TID = x.TID -- <= added here
)
SELECT TID, amt, RunningTotal = rt
FROM x
ORDER BY x.rn
OPTION (MAXRECURSION 10000);
Any compelling reason that you must use CTE instead of a simple SUM() with window function ?

Answer 2

Add Partition with TID
FIDDLE DEMO
;WITH y AS
(
SELECT TID, amt, rn = ROW_NUMBER() OVER (PARTITION BY TID ORDER BY TID)
FROM #Transactions
), x AS
(
SELECT TID, rn, amt, rt = amt
FROM y
WHERE rn = 1
UNION ALL
SELECT y.TID, y.rn, y.amt,x.rt + y.amt
FROM x INNER JOIN y
ON y.rn = x.rn + 1 AND x.TID = y.TID
)
SELECT TID, amt, RunningTotal = rt
FROM x
ORDER BY x.TID, x.rn
OPTION (MAXRECURSION 10000);

Answer 3

You dont need recursive CTE. You can simply for a PARTITION BY based approach.
SELECT tid
, AMT
, SUM(amt) OVER(PARTITION BY tid ORDER BY tid
ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW
) AS RunningTotal
FROM #Transactions
update
Sorry. Just now, went through comments.
If you have to use CTE, go with answer by #Squirrel. If you are fine with window functions, you can use the above approach.